1. Field of Invention
The present invention relates to military training equipment, and more particularly, to an improved laser transmitter mounted on a rifle for use by a soldier in war games.
2. Description of Related Art
U.S. Army regulations require a soldier to xe2x80x9czeroxe2x80x9d his or her small arms weapon twice each year. This weapon is typically an M16A1 or M16A2 rifle. The rifle is zeroed by shooting live ammunition at a target twenty-five meters away. The location of a cluster of bullet holes relative to a target reticle is observed and azimuth and elevation adjustments are made to the conventional or so-called xe2x80x9cironxe2x80x9d sights of the rifle until the bullets strike at or near the reticle with a higher frequency, thus indicating that the iron sights are correctly adjusted. The parameters of the number of degrees of azimuth and elevation are recorded by the soldier on an adhesive label applied to the rifle so that the conventional sights can be re-set if they should become misaligned, e.g. from the weapon being disassembled for cleaning or repair.
The trajectory of the bullet, as it leaves the rifle, is curved slightly downwardly due to the effects of gravity. Thus, the conventional sights of the M16A2 rifle may be adjusted to achieve a 95% xe2x80x9ckillxe2x80x9d rate at twenty-five meters and a 95% kill rate at three-hundred meters. A soldier aiming at a target between these two ranges would achieve a much lower kill rate. The geometry of a direct line of sight intersecting a curved bullet trajectory necessarily imposes this limitation on all small arms weapons.
For many years the U.S. Army has trained soldiers with a multiple integrated laser engagement system (MILES). One aspect of MILES involves a small arms laser transmitter (SAT) being affixed to the stock of a small arms weapon such as an M16A1 rifle or a machine gun. Each soldier is fitted with detectors on his or her helmet and on a body harness adapted to detect a laser xe2x80x9cbulletxe2x80x9d hit. The soldier pulls the trigger of his or her weapon to fire a blank or blanks to simulate the firing of an actual round or multiple rounds. An audio sensor or a photo-optic sensor detects the firing of the blank round(s) and simultaneously energizes a laser diode in the SAT which emits a laser beam toward the target which is in the conventional sights of the weapon.
When fitting the SAT to a rifle or machine gun barrel, in the past it has been necessary to align the transmitter so that a soldier can accurately hit a target with a short burst from the laser diode once he or she has the target located in the conventional rifle sights. According to one prior art approach, the SAT was bolted to the rifle stock and the conventional sights of the weapon were adjusted to align with the laser beam. The disadvantage of this approach is that the conventional weapon sights had to be readjusted in order to use the rifle with live rounds. Thus the rifle was rendered useless for actual combat unless and until it was zeroed. To overcome this disadvantage, later SATs incorporated mechanical linkages for changing the orientation of the laser.
Aligning a SAT has generally been performed using a fixture. One type of prior art small arms alignment fixture (SAAF) that has been used by the U.S. Army for alignment of the early MILES SAT consists of a complex array of one hundred forty-four detectors which are used in conjunction with thirty-five printed circuit boards to determine where the laser hits with respect to a target reticle. The difficulty in using this prior art target array SAAF is that the soldier aims his or her weapon at the array which is twenty-five meters away without the use of a stable platform. In many cases, the soldier fires his or her weapon in a manner which results in the aim point not being at the desired location. The fact that the array is located twenty-five meters away from the soldier also introduces visibility limitations due to snow, fog, wind and poor lighting conditions at sunrise or dusk.
Furthermore, the prior art target array SAAF calculates the number of error xe2x80x9cclicksxe2x80x9d in both azimuth and elevation. The number of clicks is then displayed on the prior art target array SAAF using four sets of electromechanical display indicators. A soldier must turn his conventional SAT""s adjustors the corresponding number of clicks in the correct direction. He or she must then aim and fire the weapon again and make additional corresponding adjustments. This iterative process continues until the soldier obtains a zero indication on the prior art target array SAAF. This is a very time consuming and tedious process due to normal aiming errors incurred each time the soldier has to reacquire the target reticle. It is not uncommon for a soldier to take fifteen minutes to align the SAT to the best of his or her ability and still not have it accurately aligned.
Not only is the alignment process utilizing the prior art target array SAAF time consuming, it also expensive because a large amount of blank ammunition must be used. The laser of a conventional SAT will not fire without a blank cartridge being ignited or by using a special dry fire trigger cable. The prior art target array SAAF does not support optical sights, different small arms weapon types, or night vision devices. Nor does the prior art array target SAAF accurately verify the laser beam energy and encoding of a received laser beam.
In response, SATs which eliminate the need to utilize a large target array have been developed by Cubic Defense Systems, Inc. and deployed by the U.S. Army as part of Cubic""s MILES 2000(copyright) training system. The exercise events and casualties are recorded, replayed and analyzed in detail during xe2x80x9cafter action reviewsxe2x80x9d (AARs). The MILES 2000 SATs are adjustable for more rapid and accurate alignment of their laser output. The transmitters feature adjustable powers and coding to enable the man-worn portion of the MILES 2000 system to discriminate between kills made by different small arms and different players.
The MILES 2000 SAT is disclosed in the aforementioned U.S. Pat. No. 5,476,385 of Parikh et. al. It uses a pair of optical wedges that are rotated to steer the laser beam and align the same with the boresight of the rifle. This approach, while achieving a reasonable degree of aligning the laser beam with the conventional sights, requires a relatively expensive construction of the MILES 2000 SAT. This is attributable to the cost of the beam steering components such as the glass wedges, stainless steel gears, shafts, drive gears, housing, etc. The components must be small in size which makes mechanical design tolerances extremely tight. Furthermore the SAT-equipped rifle must be inserted into a portable box-like MILES 2000 SAAF in order to accomplish the bore sighting in a semi-automatic fashion. See the aforementioned U.S. Pat. No. 5,410,815 of Parikh et al. The portable MILES 2000 SAAF itself is a relatively expensive device which must be calibrated.
As disclosed in the pending application referenced above, high temperature resistant adhesive has been used to avoid changes in focal length due heating of the weapon induced by firing repeated blank rounds. Such changes in focal length can severely impact the accuracy of the SAT-equipped rifle once it has been properly bore sighted. Another major problem in maintaining the accuracy of a SAT is attributable to the high accelerations induced in the SAT when a round is discharged. In the case of a machine gun, forces as high as one-thousand times the force of gravity can be generated in all three axes. This can lead to misalignment of parts inside the SAT which can either shift the laser beam away from the preferred alignment or diffuse the beam so that the accuracy of the SAT over long ranges in unacceptably diminished.
Prior attempts to design an accurate SAT have led to unduly expensive and complex solutions because they have been based on aligning the laser beam with the conventional sights of the weapon. Since the laser beam travels in an absolutely straight path, it needs to be somewhat downwardly biased in elevation to simulate the effects of gravity on the bullet. There is an inherent problem in this approach in that the laser is being aligned with the conventional sights which themselves may not be zeroed. Once the weapon is zeroed, the SAT is then misaligned. Furthermore, the whole process of aligning the SAT is unrealistic for a soldier, who should only engage in training activities which themselves mimic actual combat operations and maneuvers.
Accordingly, it would be desirable to provide a low cost small arms transmitter that can be properly aligned in a simpler and more inexpensive fashion and would thereafter maintain its accuracy in a harsh combat training environment.
Accordingly, it is the primary object of the present invention to provide an improved laser small arms transmitter (SAT) for use in simulated combat exercises.
Another object is to provide an improved SAT that can be manufactured at relatively low cost.
Another object of the present invention is to provide an improved SAT that is easier and less costly to align.
Another object of the present invention is to provide an improved SAT that will maintain its accuracy for long durations despite the high temperatures and high accelerations typically encountered in a combat training environment.
Another object of the present invention is to provide an improved method of aligning a SAT that is simpler, less expensive and more accurate than previous methods.
Another object of the present invention is to provide a SAT with greater effective range under varying temperature conditions.
Another object of the present invention is to eliminate the necessity for a soldier to align a SAT mounted on his or her small arms weapon.
Another object of the present invention is to eliminate expensive laser beam steering components in a SAT.
In accordance with the present invention, a laser small arms transmitter (SAT) includes a housing having a hollow interior and a clamp structure connected to the housing for rigidly securing the housing to a barrel of a weapon. A laser tube is rigidly mounted inside the housing. A lens is mounted in a forward portion of the laser tube and positioned in alignment with a bore in a forward side of the housing. A semiconductor laser device is mounted in a rearward segment of the laser tube. A circuit mounted inside the housing selectively energizes the semiconductor laser device to cause the same to emit a laser beam through the lens. The rear segment of the laser tube is made of a material that is permanently bendable. The rear segment of the laser tube is also dimensioned and configured so that it can be bent to align the laser beam emitted by the semiconductor laser device relative to the barrel of the weapon.
Another aspect of the present invention is a method of aligning a laser beam of a small arms transmitter to the barrel of a small arms weapon. The method first involves the step of mounting a small arms transmitter on a fixture pre-aligned with a center of a target reticle. The next step of the method involves energizing a semiconductor laser device in the small arms transmitter to cause a laser beam to be emitted thereby. The final step of the method involves aligning the semiconductor laser device so that the laser beam strikes at or near the center of the target reticle to thereby align the laser beam with the barrel of the small arms weapon to which it will be mounted.